The present invention relates to a magnetic disk drive and, more particularly, to a flying magnetic head slider capable of recording and reproducing data while flying slightly above a recording medium due to an air bearing.
A magnetic disk drive applicable to a computer as an external storage includes a magnetic head for recording and reproducing data out of a recording medium. The head is mounted on a magnetic head slider facing the recording medium and capable of flying to a preselected height above the medium. While the medium spins, the resulting viscous flow of air is born by an air bearing surface facing the medium. The slider therefore flies slightly above the medium due to an air bearing available with the air bearing surface. The head is mounted on the air outlet end portion of the air bearing surface and oriented toward the medium. During the flight of the slider, the head records or reproduces data in or out of the medium without contacting the medium.
The slider of the type described is brought to a desired track by a positioner while seeking the medium. Specifically, with such a rotary actuator type positioner, to access data, the slider seeks the medium from the innermost circumference to the outermost circumference of the track. This brings about a problem that the pressure acting on the air bearing surface depends on the radial position of the track of the medium because the velocity of the viscous flow of air depends on the radial position of the track. As a result, the flying height of the slider differs from one radial position to another radial position of the track. Moreover, the yaw angle between the direction tangential to the medium and the longitudinal axis of the slider differs from the innermost circumference to the outermost circumference. A change in yaw angle causes the air stream flowing along the air bearing surface to vary, thereby varying the pressure distribution. This also causes the flying height of the slider to fluctuate.
A change in the flying height of the slider directly translates into a change in electromagnetic transduction efficiency available with the head and thereby deteriorates a signal-to-noise ratio. To implement high density CDR (Constant Density Recording) required of a magnetic disk, it is necessary to maintain a high BPI (Bit Per Inch) over the entire track area. It is therefore extremely important to guarantee the constant flying height of the slider over the entire track area.
Technologies relating to the present invention are also disclosed in, for example, Japanese Patent Laid-Open Publication Nos. 61-160885, 3-125378 and 4-228157.